title: Morbidity before and after the diagnosis of hyperthyroidism: a nationwide register-based study.
abstract: BACKGROUND
  Hyperthyroidism has been linked with different morbidities, like atrial fibrillation, stroke and diabetes mellitus. However, our knowledge regarding the extent and temporal relation between hyperthyroidism and other diseases is fragmented. Here, we aimed at evaluating various morbidities before and after the diagnosis of hyperthyroidism.
  
  
  METHODS
  Observational cohort study. From nationwide Danish health registers 2631 hyperthyroid singletons and 375 twin pairs discordant for hyperthyroidism were identified and followed for an average of 6 years (range 0-13). Data on the occurrence of cardiovascular diseases, lung diseases, diabetes mellitus, rheumatic diseases and malignant diseases was obtained by person-to-person record linkage with the National Danish Patient Register and/or the Danish National Prescription Registry (lung diseases and diabetes mellitus). Logistic and Cox regression models were used to assess the risk of morbidity before and after the diagnosis of hyperthyroidism, respectively. All Cox regression analyses were adjusted for the degree of co-morbidity preceding the diagnosis of hyperthyroidism, using the Charlson score.
  
  
  RESULTS
  Hyperthyroid individuals had a significantly higher risk of being diagnosed with cardiovascular diseases (odds ratio (OR) 1.65; 95% confidence interval (CI): 1.45-1.87), lung diseases (OR 1.53; 95% CI: 1.29-1.60), and diabetes mellitus (OR 1.43, 95% CI: 1.20-1.72), but not with malignant diseases (OR 1.16, 95% CI: 0.99-1.36) prior to the diagnosis of hyperthyroidism. After the diagnosis of hyperthyroidism, subjects had a significantly higher risk of being diagnosed with cardiovascular diseases (hazard ratio (HR) 1.34; 95% CI: 1.15-1.56), lung diseases (HR 1.28; 95% CI: 1.10-1.49), and diabetes mellitus (HR 1.46; 95% CI: 1.16-1.84), but not with rheumatic diseases (HR 1.39, 95% CI: 0.92-2.09) or malignant diseases (HR 1.18, 95% CI 0.97-1.42).
  
  
  CONCLUSIONS
  We demonstrate a significantly increased burden of morbidity, both before and after the diagnosis of hyperthyroidism.
authors.affiliation: Department of Endocrinology and Metabolism, Odense University Hospital, Odense, Denmark. frans.hjelm.brandt.kristensen@ouh.regionsyddanmark.dk
authors.forename: Frans
authors.initials: F
authors.lastname: Brandt
authors.forename: Marianne
authors.initials: M
authors.lastname: Thvilum
authors.forename: Dorthe
authors.initials: D
authors.lastname: Almind
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.forename: Anders
authors.initials: A
authors.lastname: Green
authors.forename: Laszlo
authors.initials: L
authors.lastname: Hegedüs
authors.forename: Thomas Heiberg
authors.initials: TH
authors.lastname: Brix
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000453:epidemiology; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D003920:Diabetes Mellitus / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000175:diagnosis* / Q000453:epidemiology*; D016015:Logistic Models; D008171:Lung Diseases / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D016016:Proportional Hazards Models; D012042:Registries / Q000706:statistics & numerical data*; D013997:Time Factors